1. Field Of The Invention
This invention is directed to aminoethylation processes for producing substituted ethylene diamines; in one aspect, substituted ethylenediamines are produced by reacting oxazolidinones (also called oxazolidones) or their precursors with secondary amines or alkanolamines.
2. Description of Related Art
Prior art methods for producing ethylenediamines employ relatively expensive starting materials and result in a variety of by-products. In one typical prior art process ethylene amines are continuously produced by reacting ammonia with ethylenedichloride. Neutralization with sodium hydroxide follows, producing amines and salt. Salt separation yields a mixture of amines, water and unreacted ammonia. Distillation of the mixture produces a variety of products in the ethyleneamine family, including: ethylenediamine (EDA), diethylenetriamine (DETA), triethylenetetramine (TETA), tetraethylenepentamine (TEPA), pentaethylenehexamine (PEHA), Ethyleneamine E-100, piperazineamine mix, aminoethylpiperazine (AEP), and aminoethylethanolamine (AEEA).
The prior art discloses the reaction of hydrochloric acid with 2-oxazolidinone to produce 2-chloro-ethyleneamine hydrochloride and carbon dioxide. In another known reaction, aziridine and aziridine salts react with hydrochloric acid to produce ethylenediamines (see Scheme 1); however, evidence of toxic and carcinogenic properties of these reagents severely limit their use. In various prior art processes, amines (primary, aliphatic, aromatic) reacted with oxazolidinones to produce substituted ureas. ##STR1##
Although electrophiles such as carboxylic and sulfonic acids or carboxylic acid chlorides can undergo decarboxylative ring opening at the C-5 position of 2-oxazolidinone to produce substituted ethylenediamines (see equations 1 and 2), more recent prior art work has shown that aniline salts and thiophenols also produce substituted ethylenediamines. For example, aniline hydrochloride salts reacted with various 2-oxazolidinone to give the ethylenediamines shown in equation 2. ##STR2## No ring opening reaction occurred in the prior art process using either 4,4-dimethyl-2-oxazolidinone (1, below) or 5-ethyl-2-oxazolidinone (2, below) with aniline hydrochloride. ##STR3##
It has been shown that the reaction of oxazolidinones with aliphatic or aromatic amines affords N-(2-hydroxyethyl)ureas (3, below) and imidazolidinones (4, below) via attack at the C-2 ring carbonyl position of the oxazolidinone (see equation 3). Imidazolidinones are obtained by dehydration of the urea due to the higher temperatures required for the reaction of aromatic amines with the oxazolidinone. ##STR4##
According to certain prior art, aliphatic amines and hydrochloride salts of aliphatic amines do not ring open oxazolidinones to yield ethylenediamines. For example, the reaction of 2-oxazolidinone with n-BuNH.sub.2 .multidot.HCl in 2-(2-methoxyethoxy)ethanol at 160.degree. C. failed to give any diamine product after 12 hours. Starting amine and oxazolidinone were recovered unchanged. The prior art explanation is that the reluctance of aliphatic amine salts to promote ring opening is due to their being less acidic than aromatic amine salts (pKa's of 5 for aromatic vs. pKa's of 10 for aliphatic amine salts; "pKa" is the pH at the half-neutralization point when the amine is reacted with acid; it is the logarithm of the amine protonation equilibrium reaction constant) and therefore are not strong enough acids to initiate the reaction. The prior art teaches than the degradation of diethanolamine with carbon dioxide is kinetically consistent with an oxazolidinone intermediate mechanism and discloses that N-(2-hydroxyethyl)oxasolidinone (HEOD) is involved in the formation of N,N,N'-tris(2-hydroxyethyl)- ethylenediamine (THEED) when diethanolamine (a secondary alkanolamine) is reacted with HEOD in the presence of carbon dioxide.